1. Field of the Invention
This invention relates to segment display systems. In particular, this invention pertains to segment display systems which provide predetermined pattern displays resulting from the conversion of long wave ultraviolet photons into visible light energy through excitation of flourescent material coatings such as synthetic Phosphors. More in particular, this invention relates to segment display systems wherein ultraviolet radiation is produced by the ionization of metal atoms through an electric field applied internal to generally linearly directed slot through openings to form hollow cathodes having a metallic sidewall coating. Further, this invention pertains to segment display systems where long wave ultraviolet photons are directed in a controlled manner from a cathode mechanism to an impingement on fluorescent material compositions. More in particular, this invention relates to segment display systems wherein visual segment areas are formed in a predetermined pattern such as a seven or fourteen segment display, wherein such display visualizes numeric and alphabet type characters.
2. Prior Art
Segment display systems are known in the art. Various segment display systems rely on light emitting diode, or liquid crystal diode actuation. Other types of display systems rely on gas discharge and are known in the art.
It is believed that the various gas discharge display systems of the prior art are the closest art to the subject segment display system. The subject display system is not classified as a gas discharge display, however, such prior art gas discharge systems generally rely on a multiplicity of plasma displays which may be attained either as alphanumeric displays having generally linearly or arcuately segmented cathodes or dot matrices. Such prior art systems are generally based on the ionizatior of a noble gas or gas mixtures. In such prior art systems, the ionization occurs generally between flat and parallel electrodes with generally the anode electrode being transparent to light generated in the neighborhood of the cathode electrode.
Various disadvantages are found when such prior art gas discharge display systems are used. In such prior art gas discharge systems, the visible glow from the cathode surface is visibly stable only if the totality of the surface area of the cathode is uniformly covered by the glow and the cathode surface has uniform properties. In the event that either of these conditions is not found, the visible light will provide a flickering effect which is deleterious to an observer.
Another disadvantage of such prior art gas discharge systems is that the operating life of such is dependent upon the sputtering rate from the cathode electrode. This is generally due to the fact that the sputtering of the material from the cathode electrode deposits itself on the anode electrode. This reduces the anode electrode's transparency.
In such prior art systems, the sputtering also reduces the gas pressure by physical adsorption of the filling gas. In order to provide an acceptable operating light of such prior art systems, they are generally operated at lower than the maximum current density, which results in less than optimum light output.
Other prior art gas discharge displays using hollow cathodes are known in the art, and are represented in U.S. Pat. Nos. 3,882,342 and 4,021,695. As in the case of other prior art, such references use the back filling gas to produce ultraviolet radiation in the positive column. This type of approach suffers from the same disadvantages as has been previously described. In opposition, the subject display system does not require the gaseous medium to produce a measurable amount of ultraviolet energy. The gaseous medium in the subject display system is used to sputter the atoms of metal from the cathode and the applied electrical field ionizes such atoms to produce an intense utltraviolet glow. Such an ultraviolet glow produced from the ionization of the metal atoms is greater than the intensity of the ultraviolet glow from the gaseous medium.